ORA-19505 / 27037 while copying files from ASM using DBMS_FILE_TRANSFER

Hi,
We have a 2 node RAC system with database files on ASM. We are trying to copy the data files from ASM to a network / local file system using DBMS_FILE_TRANSFER but keep getting ORA-19595,27037 and 06512

Here is how we are doing it

SQL> create tablespace test;
Tablespace created.

SQL> select file_name from dba_data_files where tablespace_name='TEST';

FILE_NAME
--------------------------------------------------------------------------------
+DATA/isfstag/datafile/test.262.686076693


SQL> create directory dfdir as '/+DATA/isfstag/datafile';
Directory created.

SQL> create directory destdir as '/home/oracle/test';
Directory created.


SQL> alter tablespace test offline normal;

Tablespace altered.

SQL> begin